Myelin is a fatty material that coats, protects, and insulates nerves, enabling them to quickly conduct impulses between the brain and different parts of the body. Myelin coats the nerves of both the CNS and PNS.
Spaces between the sections of myelin are called nodes of Ranvier. As the brain sends messages through the nerves of the spinal cord, the impulses jump from node to node. Myelin prevents these impulses from escaping from the nerve at the wrong point.
Myelin also contains proteins that can be targeted by the immune system. In multiple sclerosis, T cells from the body's own immune system attack and destroy the myelin sheath, leaving the nerve cell fibers unprotected. The nerves are not as able to pass messages from the brain to the other body parts, or they are delayed or distorted, and the messages the brain receives may be misinterpreted.
Myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also called plaques. These plaques can be identified by (MRI), a technique that helps assess and monitor the progression of multiple sclerosis.
Central Nervous System (CNS) - the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord.
Brain - The major processing unit of the nervous system.
Spinal Cord - has certain processing ability such as that of spinal locomotion and can process reflexes
Peripheral Nervous System (PNS) - The part of the nervous system that consists of the nerves and ganglia on the outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system (CNS) to the limbs and organs, essentially serving as a communication relay going back and forth between the brain and the extremities.
Sensory (Afferent) Division - Neurons that carry nerve impulses from sensory receptors or sense organs toward the central nervous system
Motor (Efferent) Division - Neurons that carry nerve impulses away from the central nervous system toward the peripheral effector organs (mainly muscles and glands)
Somatic Division - The part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The somatic division consists of afferent nerves and efferent nerves.
Autonomic Division - The part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes.
Sympathetic Division - It's general action is to mobilize the body's nervous system fight-or-flight response; it is also constantly active at a basal level to maintain homeostasis.
Parasympathetic Division - It is responsible for stimulation of "rest-and-digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation.
Frontal lobe: Higher mental functions including concentration, planning, judgment, emotional expression, creativity, and inhibition
Temporal Lobe: Association Area including short term memory, Equilibrium and emotion.
Occipital Lobe: visual area: sight, image recognition and image perception.
Parietal Lobe: Sensory Area: sensation from muscles and skin
Neocortex: Motor Functions: Coordination of movement, balance and equilibrium, posture.
thalamus: Relay and processing centers for sensory information
hypothalamus: Centers Controlling emotions, autonomic functions and hormone production
amygdala: center for emotions, emotional behavior and Motivation
hippocampus: Center for memory forming, organizing and storing.
midbrain: Processing of visual and auditory data, Generation of reflexive somatic motor responses, Maintenance of consciousness
pons: Relays sensory information to the cerebellum and thalamus, Subconscious somatic and visceral motor centers
medulla: Relays sensory information to the thalamus, Autonomic centers for regulation of visceral functions such as cardiovascular respiratory and digestive activities.
In physiology, a stimulus (plural stimuli) is a detectable change in the internal or external environment. The ability of anorganism or organ to respond to external stimuli is called sensitivity. When a stimulus is applied to a sensory receptor, it normally elicits or influences a reflex via stimulus transduction. These sensory receptors can receive information from outside the body, as in touch receptors found in the skin or light receptors in the eye, as well as from inside the body, as in chemoreceptors and mechanorceptors. An internal stimulus is often the first component of a homeostatic control system. External stimuli are capable of producing systemic responses throughout the body, as in the fight-or-flight response. In order for a stimulus to be detected with high probability, its level must exceed the absolute threshold; if a signal does reach threshold, the information is transmitted to the central nervous system (CNS), where it is integrated and a decision on how to react is made. Although stimuli commonly cause the body to respond, it is the CNS that finally determines whether a signal causes a reaction or not.